The present invention relates to pavement markers which are recessed into the pavement surface. The pavement marker is designed for use in areas that receive snowfall and hence, is designed to be snowplowable while resistant to damage from the action of the snowplow.
Pavement markers, as used herein, are mechanisms for setting a reflective element in or on the roadbed so that the light of the vehicle headlamps can be reflected back to the driver. The source of the reflection delineates edges of lanes, on/off ramps, and other features of the roadbed. These pavement markers are used in addition to, or instead of, standard paint, epoxy, or thermoplastic striping.
Pavement markers are generally broken down into two typesxe2x80x94sun country or snowplowable. Sun country markers are used where snow is either not present or an infrequent event, and thus their design does not have to take into account the operation of a snowplow to clear the traffic lanes. Snowplowable markers, as the name implies, are designed to be placed on roadbeds where snowplows operate. The markers are designed to accommodate the action of snowplow blades which can be a major source of damage to the pavement marker and its reflective element. Damage occurs because the snowplow blade is traveling at approximately traffic speeds and contacts the portion of the pavement marker above the pavement level. Because of the considerable mass of the snowplow blade, its momentum causes a jolt that is felt by the driver as the blade is guided up and over the marker so that it avoids impacting the reflective element. The jolt results from the resistance of the pavement marker and the pavement to the impact of the snowplow blade. In addition to transferring energy back to the snowplow truck and driver, the jolt also transfers energy to the pavement marker. If sufficient energy is transferred to the pavement marker, the pavement marker can be literally ripped out of the pavement. Snowplows may also damage the pavement markers by having the leading tip of the blade enter the marker at such a point that the blade is not guided over the marker, but rather impacts the reflector directly. At highway plowing speed the snowplow blade does not immediately return to pavement level. Rather, the blade travels vertically before dropping to pavement level, thus leaving transverse strips or patches of unplowed snow.
An example of a prior art snowplowable pavement marker is shown in U.S. Pat. No. 4,195,945. These type of markers generally have an H pattern when viewed in a plan view. The legs of the H are made up of ramps which are designed to guide the snowplow blade up and over the centrally mounted reflector element. These prior art pavement marker bases are designed to be placed into a groove in the pavement which is cut usually by means of a circular saw. The groove is approximately the length of the pavement marker. The groove is arcuate from the action of the rotating sawblades. The pavement marker is then placed within the groove and adhered to the pavement through the use of epoxy. A variation of that same type of marker is seen in U.S. Pat. No. 5,277,513 which calls for the same basic design with only minor dimensional changes. In cases of the prior art pavement markers such as referenced immediately above, the reflector is carried at or above the pavement level as determined by the web which interconnects the ramps on either side of the marker. The leading edge of the web is dimensioned to be at or above the surrounding pavement level. In these prior art designs it is recognized that there was a continuing problem to reduce the overall height of the reflector of the pavement marker to a minimum level above the roadway while still maintaining the reflector above the roadway surface. See, for example, the ""513 patent at Col. 2. The impetus to maintain the reflector above the roadway surface came from the recognition that the reflector needed to be exposed to the light from the oncoming headlights in order to have some light to reflect back. Greater height above the roadway provided this. Working against this goal, however, was the recognition that the higher the pavement marker was above the roadway, the more of an obstacle it presented to an oncoming snowplow, and the greater damage it would receive from impact with the snowplow. See, ibid. Therefore, the prior art as represented by the above references sought to change the various dimensions such as ramp angles, widths, heights, etc. to force the snowplow blade over the reflector while still keeping the leading edge of the web which carried the reflector at or above the level of the surrounding pavement.
Another type of prior art consisted of grooves cut in the pavement where the depths of the grooves increased in the direction of vehicle travel. At the bottom of the groove, a retroreflector was mounted below grade level. An example showing a two way snowplowable marker is shown in U.S. Pat. No. 4,395,155 to Bartolotti. This reflector could also be mounted at one end of the groove for a one-way plowable marker. While providing snowplow protection, this installation has had limited use for a variety of reasons, including the filling of the groove with road debris such as dirt, sand, eroded pavement, and the fact that the reflector was below pavement level served to limit the reflective light to the motorist. As stated in the patent, the groove cut in the pavement was narrower than the width of vehicle tires to prevent destructive contact between the vehicle tires and the reflector.
The objectives of the invention are:
to provide a pavement marker that is resistant to damage from snowplow blades and protects the retroreflector;
to provide a pavement marker which is self-cleaning to resist blocking of the retroreflector from oncoming light due to road debris collecting in front of or on the reflector;
to provide a pavement marker that is of very low profile having a minimum amount of the marker protruding above the surface of the pavement;
to provide a pavement marker that is easily installed, using conventional equipment and techniques;
to provide a pavement marker that can utilize standard or existing retroreflector elements;
to provide a pavement marker that has the reflector carrying web between the ramps initially below the pavement surface so as to reduce snowplow blade impact while allowing openess to oncoming light;
to provide a pavement marker with the web element or the portion between the ramps entirely below the pavement surface;
to provide a pavement marker for installation at the end of long approach grooves cut in the pavement such as found in several northeastern states;
to provide a pavement marker that minimizes use of installation adhesive, as well as minimizing unsightly overflow of adhesive; and
to provide a pavement marker whereby rail height is reduced by allocating structural integrity responsibility to nearby structures.
The above advantages are obtained and several others will become apparent from the description of the present invention. The present invention includes a low profile pavement marker base member for use in snow areas on which a retroreflector is mounted to provide reflected light back to an oncoming vehicle. The pavement marker base is designed to be mounted within a deepened section of a groove in the pavement located just before the front edge of the pavement marker base. The front edge of the pavement marker, and especially its reflector carrying web, is designed to be mounted below the pavement level so that oncoming light traveling down the groove continues into the pavement marker base between the ramps and impinges upon the retroreflector. In one preferred embodiment the pavement marker is a one way marker, i.e. it is designed to receive the snowplow blade from one direction only. In an alternate embodiment, the marker can be two-way by replicating the ramps and reflective element as shown in FIG. 5, although the overall length will be less than twice the length of a one way reflector and other dimensions will have to be adjusted accordingly. For example, the ramp angle will have to be steeper to bring the plow blade over the reflector in a shorter distance, but the beginning of the web will still be below pavement level.
The pavement marker includes a base member with two longitudinally extending and laterally spaced apart ramps. The ramps are designed to start at a level below pavement and extend above the pavement level to help guide the snowplow blade up and over the retroreflector. The bottom side of the reflector base has a series of cleats or treads on either side to help anchor the base into a prepared roadway through the use of epoxy. The cleats help prevent dislocation of the pavement marker base relative to the roadway. Positioning tabs can be included on either side of the pavement marker base to align the marker relative to the surrounding pavement. The retroflector is carried in a pocket on the web which preferably spans the ramps along their entire length. The proper placement of the marker will put the retroreflector starting at a level below the pavement extending to a level above the surrounding pavement, but still protected by the ramps of the pavement marker base from the snowplow blade. The reflector will be exposed to light from both above pavement level and light traveling down the cut groove.
The combined pavement marker base and retroreflector is designed to be placed in a groove cut in the pavement. The pavement marker is designed for a groove that is cut with a long approach, i.e. started several marker lengths before the position where the casting will actually be placed. The length of the groove is designed in part to allow more light to impinge upon the retroreflector as explained in more detail below. The retroreflector is adhered to the base by use of an adhesive and the marker is adhered to the pavement with adhesive such as epoxy.